In a conventional structure for attachment of a battery pack to a main body 101 of an electric power tool, as shown in FIG. 9 for example, the battery pack 102 includes manipulation portions 112 and engaging portions 111 at its lateral sides and the main body 101 of the electric power tool is provided with engaged portions 110 at its lateral sides, which are engaged with the corresponding engaging portions 111 of the battery pack 102. The manipulation portions 112 can be pushed inwardly and, by pushing the manipulation portions 112 inwardly, the engaging portions 111 are moved inwardly to be disengaged from the corresponding engaged portions 110 (see, e.g., Japanese Patent Laid-open Application No. H08-229852).
In the meantime, in case a movement stroke of the engaging portion 111 needs to be increased to obtain reliable engagement and disengagement of the engaging portion 11 with the engaged portion 110, it is considered that the distance between the engaging portion 111 and the manipulation portion 112 is set long. In the conventional case described above, if the distance between the engaging portion 111 and the manipulation portion 112 is set long, the vertical length of the battery pack 102 becomes increased in proportion thereto. Recently, there are attempts to reduce the vertical thickness of the battery pack by placing rechargeable cells horizontally. However, in case the structure shown in FIG. 9 is employed for attachment of the battery pack to the electric power tool main body, it may hinder efforts to reduce the vertical thickness of the battery pack.